Plant for the electrolysis of alkali salt solutions



19% c. DEPREZ ET AL. w fi PLANT FOR THE ELECTROLYSIS OF ALKALI SALT SOLUTIONS Mpxrill 1.1L

Filed Feb. 27, 1947 iNvzzw-ons A TTOENE Y Patented Apr. 25, 11959 STATES PLANT FOR THE ELECTBOLYSIS 0F ALKALI SALT SOLUTIGN S Belgian company Application February 27, 1947, Serial No. 731,264 In Belgium March 2, 1946 1 Claim. i

This invention relates to cells for the electrolysis of aqueous solution of alkali salts. These cells usually comprise two shallow troughs arranged side by side, the first of which is the electrolytic cell prope serving to produce alkali amalgam which thereafter is decomposed in the second cell. Such arrangement take up a great deal of space and it requires extensive current conductors.

It has been endeavoured to reduce these inconveniences by making the decomposition cell in the shape of a scrubber or of a vertical cell arranged at the end of the electrolysis cell, but in both cases it is necessary to provide a special pipe for returning the mercury to the inlet of the electrolysis cell. With modern cells which use current of high intensity and are of considerable length (of the order of 50 feet) the length of this pipe is responsible for increasing the amount of mercury in use; in order to reduce the expense, it has been proposed to reduce the diameter of the pipe to a minimum but it i then difficult to avoid obstructions.

An object of our present invention is to avoid these inconveniences. To that end the electrolytic cell and the decomposition cell are placed one above the other thereby reducing by one half the floor space taken up, while keeping the advantages of the two original elements.

It may be of advantage to increase the vertical distance between th superposed cells, so as to suit the work in a two-story electrolysis hall, one story being reserved for the production of the alkali amalgam and the other for the decomposition thereof.

In order that the height of the mercury column due to the difference between the levels of both floors will not be an inconvenience, we use in accordance with our invention the hydrostatic effeet to cause the element at the lower level to operate under pressure. The direct advantage of this arrangement is that the hydrogen or the chlorine gas, as the case may be, is available under pressure and may be so distributed for con-= sumption without the use Of a special pump or compressor.

For conveying the mercury of the amalgam from the lower level to the higher level a lifting device is necessary, which should be of a power in.

proportion. to the difference between said levels. It is however possible, in carrying out the invention, to use the same liftin device whatever be the height to be overcome. To that end, we introduce the mercury (or the amalgam) under pressure into an upward column according to the principle of communicating vessels, and in that column we insert the lifting device so that it only has to overcome the level difierences due to the respective slopes of the two cells.

The accompanying drawing illustrates diagrammatically by way of example an arrangement according to our invention.

In a horizontal electrode drawing, a is a horizontal electrode electrolytic cell, and b the amalgam decomposition cell, which are connected for the purpose of circulation of the mercury, by the downward column or passageway c and the upward column or passageway d. The trough of cell I) being under a pressure measured. by the height H of column 0, the mercury by virtue of the principle of communicating vessels, ascends in the column d up to the level N, the columns or passageways c and d and the decomposition cell forming a U-shaped hydrostatic system, and the lifting device 6 has to overcome, in addition to the resistance represented by it, only the sum of pressures measured by the heights hl, hz respectively corresponding to the slopes of the two troughs, as is the case when the two cells are placed side by side.

In the example illustrated, hydrogen is delivered under pressure by the decomposition cell. If it is desired to obtain chlorine gas under pressure, the electrolytic cell a will of course be located at the lower level.

The invention is of as much advantage when a single decomposition cell is used for decomposing amalgam produced by a plurality of electrolytic cells, the decomposition cell then being preferably located at the lower level; a single lifting device may be used to convey the mercury to said plurality of cells.

We claim:

In a plant for the electrolysis of alkali salt solutions with a mercury cathode, the combination of an elongated horizontal elelectrode electrolytic cell which is slightly inclined in one direction, an elongated horizontal electrode decomposition cell disposed directly beneath the electrolytic cell and slightly inclined in the opposite direction, a passageway connecting the bottom of the lower end of the electrolytic cell with the bottom of the higher end of the decomposition cell, and a passageway connecting the bottom of the lower end of the decomposition cell with the bottom of the higher end of the electrolytic cell, the decomposition cell being a pressure cell and forming with said passageways a U-shaped hydrostatic system in which a head of mercury amalgam in aeozzeee E3 4 the passageway leading from the lower end of the REFERENCES CITED electrolytic cell to the decomposition cell lifts the The 1.01] Owing erenc es ar e of record in the mercury in the second passageway substantially m of i g to the same height, the decomposition cell eperating underpressure equal ts'said head of mer- 5 UNITED STATESJPATENTS cury, and a liftingtdevice inserted in the second Numbey Name Date passageway at a point just below that to which 913,370 Rink Apr. 13, 1909 the mercury is lifted by hydrostatic pressure for 2,232,123 Muller Feb. 18, 1941 lifting the mercury from said point to the higher end of the electrolytic cell. 10 FOREIGN PATENTS Number Country Date CHARLES .DEPREZ. 223106 Great Britain Dec. 8, 1900 ALEXIS BASILEWSKY. 8,529 Denmark May 28, 1906 

